In the history of Princeton, we have all heard of Albert Einstein, Robert Oppenheimer, and Alan Turing. But what about a Princetonian philosopher?
David Kellogg Lewis (1941-2001) was a professor in the Princeton Department of Philosophy. His work contributed to multiple fields of philosophy, but he stood out most in metaphysics, in which he was broadly seen as the most prominent systemic thinker of his time. His work exemplified the “analytic tradition” in philosophy–a style of philosophy concerned with finding truth through formal logic, conceptual clarity, and argumentative precision. Professor Lewis was also known for an undergraduate seminar called Metaphysics (Philosophy 318), where he introduced students to the many difficult and exciting questions of modern metaphysics.
While the esteemed professor is no longer with us, I was elated to discover that his metaphysics seminar is still taught 25 years later. Junior fall, I took Metaphysics (still, per tradition, titled Philosophy 318), a three-hour discussion seminar on Wednesdays now taught by Professors David Builes and Michele Odisseas Impagnatiello. While I had touched on the subject in other classes, I still barely had a grasp on what metaphysics was beyond a field concerning questions that seemed…metaphysical. By December, though, Metaphysics had changed my life.
The syllabus listed a summary of the course with a new topic each week as follows:
- Abstracts
- Materials
- Critiques of metaphysics
- Social and natural kinds
- Race and gender
- Fundamentality
- Persistence
- Time
- Modality
- Causation
Most interesting to me was fundamentality, modality, and causation. I’ve since found myself applying these aspects of metaphysics to contexts beyond philosophy and academics. Together, they reorganized my concept of what things are, how things exist, and why things happen.
During the fundamentality week, we thought about what makes something more fundamental than something else. One account of this is captured by the concept of grounding advanced by Professor Gideon Rosen, a current Princeton Philosophy professor who teaches “Introduction to Metaphysics and Epistemology”:
A is grounded in B if A…
(1) obtains in virtue of B
(2) obtains because of B
(3) is grounded in B.
This articulation of grounding allows us to express that something is metaphysically prior to something else. For instance, if you are an Aristotelian, your identity as an Aristotelian is grounded in your philosophical alignment with his ideas. You are an Aristotelian in virtue of your philosophy. Grounding and fundamentality also beg a deeper (more fundamental, if you will) reflection on the layers of reality. Is there a basic, most fundamental layer, or is it turtles all the way down?
Three weeks later, we learned about modality. Modality is a field of philosophy concerning logical propositions about possibility, impossibility, necessity, and contingency. Studying modality involves thinking about what is true, what could be true, and what must be true. Aspects of modality also venture from metaphysics into actual physics (not to say that philosophy isn’t real!). Professor Lewis proposed a theory of modal realism: the belief that all possible worlds do in fact exist and are just as real as the actual world. Let’s test this out. Does the possible world where I don’t enjoy metaphysics exist? Yes. Does the possible world where you read this and immediately decide to take Metaphysics exist? Yes. For the modal realist, literally every possible world exists. Lewis argued that modal realism should be accepted because of the advantages it provides in explaining counterfactuals, properties, and beliefs (more on this here).
The last week covered causation. I started with the same question as everyone else: what more could be said about causation? If I enrolled in Metaphysics, then I caused my enrollment in Metaphysics. Etc. Obviously. But turns out it’s not so obvious to rigorously define a cause. Offered on the table were three competing theories of defining causation:
(1) Regularity (2) Counterfactuals (3) Process.
The Regularity Theory claims: A is caused by B if A regularly follows B.
This seems reasonable and safe, at least. Consider, though, the fact that you (probably) wake up every morning sometime after the sun rises. But more likely it’s your alarm clock and not the sun waking you up. So maybe not quite. Demonstrably, regularity can occur by coincidence or correlation.
The Counterfactual Theory goes as follows: A causes B if, in general, if A had not happened, B would not have happened.
This seems to solve the problems of coincidence and mere correlation. Still, it cannot escape the classic problem of preemption. Consider that Suzy throws a rock and breaks the window. Billy has also thrown a rock, which would have broken the window if Suzy did not throw her rock. Per the counterfactual test, we ask: if Suzy had not thrown the rock, would the window still have been broken? Yes, it would have. Then, according to Counterfactual Theory, Suzy was not the cause of the window’s breaking because it would have been broken even had she not thrown the rock. But Suzy certainly seems like the cause. She threw the rock and broke the window. There are ways to attempt to get around this in defense of the theory, one of which I ended up proposing on my final exam, but you can see how there are apparent gaps. So, while tempting, the Counterfactual Theory can’t provide a perfect account of causation.
The rock and window bridge well into the Process Theory, which is something to the effect of: A causes B when there is some physical process linking A to B. This often involves the transfer of some conserved quantity like energy, momentum, or charge, like a pool ball knocking another into motion. But while the Process Theory seems to isolate causes to what occurs in the real, physical world, it can’t explain more abstract or mental causation. If reading this makes you take Metaphysics in the fall, I’d say real causation is happening, but there’s no pool ball bouncing around to explain it. Thus, causation is irreducible to physics alone.
These are just some of the many ideas covered in Metaphysics, which I found to be not only intellectually stimulating but also conducive towards becoming a more exacting thinker. And while I’ve heard many of my classmates lament about the abstract nature of philosophy and specifically metaphysics (understandably), I find the study of metaphysics to be practical, sharpening, and perhaps more urgent than ever in the modern day. The very trait that Professor Lewis once astounded the world with is no trivial thing to master: the ability to deconstruct, examine, and defend an argument with precision. But the epistemological foundation available in metaphysics–grasping relations like grounding, possibility, and causation–are powerful and perhaps even necessary tools to approach the biggest problems we face.
Consider the last presidential election. If you follow politics, you’ve probably heard all sorts of singular claims about what caused American voters to choose this result. Racism. Sexism. Populism. Policy. Immigration. And while all these probably had some influence, I find it quite unlikely–and empirically unsupported–to say that any one had significant causal influence on the outcome. Rather, polling and later analysis has shown that economic anxiety from years of inflation and high prices was likely the primary cause of voters defecting from the incumbent party, matching a global trend of pandemic-induced economic problems and subsequent incumbent ousting. Still, political discourse is dominated by simple, one-directional claims of causation. The progressive left blames the moderate left’s moderation. The moderate left blames the progressive left’s progressivism. And so on. This doesn’t really get us anywhere.
Accordingly, while I’m not sure what to call this norm of political discourse, it is certainly nothing close to the analytic tradition of philosophy. And electoral politics is only one example of a domain with real stakes where many common beliefs and claims lack a firm, logically-reasoned basis. The emergent problems of artificial intelligence, nuclear weapons, ecological governance, and more are difficult problems which require hard thinking to even understand, let alone solve; one cannot fix a problem first without grasping what it is. Thus, it is my contention that any student committed to tackling something of weight should learn and think about metaphysics.
Whether you are a Princetonian, prospective student, or simply a reader interested in philosophy, I hope I’ve made a convincing case of why you should study metaphysics either formally or in your own time. Metaphysics has provided me with a new framework and vocabulary for seeing everything from mundane matters to global crises. It’s a field of philosophy that I wish more people would take seriously. I believe sincerely that any large and complex endeavor can only benefit from starting with first principles.